As a graduate of Holland Hall, I can tell you all the statistics... something like 99 percent of all graduates go on to complete college, it's one of the best private schools in the country (top 20), etc.
And it's absolutely fantastic. Your kids are going to learn a bunch. But be prepared for the "rich kid" atmosphere... there's tremendous social pressure to wear the right socks, the right shoes, etc. Even though everyone wears uniforms, the kids find a way to find out who's rich and who isn't.
At $12,000 a year, it's certainally the best school, but depending on your house finances, may not be the best school for the money. If you have a kid in K-8, Trinity is about 1/4th the cost and is a excelent school. Or other cheaper options are Victory and Bishop Kelly.
But if you want the absolute best, Holland Hall is probably it.